Change the JSON schema for the security_rule Kibana asset

[rw-access]

Issues

Realized in elastic/integrations#797 and some EPM observations that this isn't structured like other Kibana assets. EPM expects Kibana assets to look like this:

{
  "id": "Whatever the object ID string is, not necessarily enforced as UUID",

  // optional references whatever these are
  "references": null || [],

  // optional info that we don't need
  "migrationVersion": null || {}, 

  // this is where the data is ultimately stored
  "attributes": { ... },

  // type of asset that matches the folder
  "type": "security_rule";
}

We don't have to make attributes internally consistent with other saved objects, but we might want to.

We can still write our own installer in EPM anyway. See the reference on AssetInstallers to see how index patterns are installed separately from other assets.

Summary

References:

• ArchiveAsset type defiinition
• createSavedObjectKibanaAsset which fills in defaults for missing fields, shows us which ones can be omitted
• AssetInstallers where each KibanaAssetType defines how it's installed

[brokensound77]

Just the one requested change, then LGTM